1. Field of the Invention
The present invention relates to the field of accessories for machine tools, with digital control, machining centers, flexible cells and workshops, and it relates to a tool holder provided with a damping means.
2. Background Art
Tool holders tend to vibrate, because of their very construction, which has a detrimental effect on their proper functioning. There is an increase in this tendency to vibrate, particularly because the operating speeds of current machine tools are constantly becoming faster.
To overcome these disadvantages, it has been proposed to provide the tool holders with an oscillation damping device that allows an adaptation of their rigidity to the work conditions.
To this effect, a device is currently known, notably from U.S. Pat. No. 3,447,402, which consists essentially of a damping weight that is installed in an axial housing, and held in the latter by clamping between elastically deformable masses, where the regulation of the stiffness is carried out through the intermediary of a spring-loaded abutment means, and the calibration of this device itself can be regulated through the intermediary of a screw device.
Moreover, from FR-A-2 173 957, an adjustable damping device for machine tools is known, which consists of a damping device which is placed in an axial hole of a tool holder arbor, and which is connected to this arbor through the intermediary of annular elastic elements that are mounted on conical ends of the damping device, and can be compressed between said ends, to regulate the rigidity.
EP-A-0 571 490 describes another damping device, which consists of a central cylindrical support which is housed in the body of the tool holder, and on which a damping body is mounted. This damping body is connected to the central cylindrical support through the intermediary of elastic elements which are arranged in the ends of the damping bodies, and held through the intermediary of gaskets that are connected to the central support. A similar device is described in EP-A-1 248 692.
In all these known devices, the damping device is held in the axial hole by action on the ends of the device through the intermediary of elastically deformable elements; however, this is achieved only by action on said ends, without any contact between said elastically deformable elements and the generator of the damping device (U.S. Pat. No. 3,447,402 and FR-A-2 173 957). The two documents that describe the use of a central cylindrical support also do not provide for any contact between the generator of the damping device and the elastically deformable element, which, moreover, would be in contact with the housing of the damping device.
As a result, such a damping device can act on the rigidity of an arbor only at its ends, so that the damping tends to occur axially, and can thus not be optimal.